In general, in a clutch unit using engagement elements such as cylindrical rollers or balls, a clutch section is arranged between an input member and an output member. The clutch section is configured to engage and disengage the engagement elements, such as cylindrical rollers or balls, between the input member and the output member, to thereby control transmission and interruption of a rotational torque.
The applicant of the present invention has previously proposed a clutch unit to be built into, for example, an automobile seat-lifter section for vertically adjusting a seat through lever operation. This clutch unit includes a lever-side clutch section to which a rotational torque is to be input through lever operation, and a brake-side clutch section for transmitting the rotational torque from the lever-side clutch section to an output side and interrupting a rotational torque to be reversely input from the output side (see, for example, Patent Literature 1).
FIG. 32 is a sectional view illustrating an overall structure of the above-mentioned related-art clutch unit disclosed in Patent Literature 1. FIG. 33 illustrates a cross section of the lever-side clutch section taken along the line E-E of FIG. 32. FIG. 34 illustrates a cross section of the brake-side clutch section taken along the line F-F of FIG. 32.
As illustrated in FIGS. 32 and 33, a lever-side clutch section 111 mainly includes a lever-side outer ring 114 to which a rotational torque is to be input through lever operation, an inner ring 115 for transmitting the rotational torque from the lever-side outer ring 114 to a brake-side clutch section 112, a plurality of cylindrical rollers 116 for controlling transmission and interruption of the rotational torque from the lever-side outer ring 114 through engagement and disengagement with respect to wedge gaps 120 formed between the lever-side outer ring 114 and the inner ring 115, a cage 117 for retaining the cylindrical rollers 116 at predetermined circumferential intervals, an inner centering spring 118 for accumulating an elastic force obtained by the rotational torque from the lever-side outer ring 114 and restoring the cage 117 to a neutral state with the accumulated elastic force through releasing of the rotational torque, and an outer centering spring 119 for accumulating an elastic force obtained by the rotational torque from the lever-side outer ring 114 and restoring the lever-side outer ring 114 to a neutral state with the accumulated elastic force through releasing of the rotational torque.
As illustrated in FIGS. 32 and 34, the brake-side clutch section 112 mainly includes the inner ring 115 to which a rotational torque is to be input from the lever-side clutch section 111, a brake-side outer ring 123 restricted in rotation, an output shaft 122 from which the rotational torque is to be output, a plurality of pairs of cylindrical rollers 127 for controlling transmission of the rotational torque from the inner ring 115 and interruption of a rotational torque from the output shaft 122 through engagement and disengagement with respect to wedge gaps 126 formed between the brake-side outer ring 123 and the output shaft 122, and plate springs 128 each having an N-shape in cross section and being inserted between the cylindrical rollers 127 of each pair, for imparting a repulsive force to the cylindrical rollers 127.
In the lever-side clutch section 111 having the above-mentioned structure, when the rotational torque is input to the lever-side outer ring 114, the cylindrical rollers 116 are engaged into the wedge gaps 120 formed between the lever-side outer ring 114 and the inner ring 115, and the inner ring 115 is rotated with the rotational torque transmitted to the inner ring 115 via the cylindrical rollers 116. At this time, elastic forces are accumulated in both the centering springs 118 and 119 along with the rotation of the lever-side outer ring 114 and the cage 117. When the rotational torque is no longer input, the lever-side outer ring 114 and the cage 117 are restored to their neutral states with the elastic forces of both the centering springs 118 and 119, whereas the inner ring 115 is maintained at the given rotational position. Accordingly, the inner ring 115 is rotated in an inching manner through repetitive rotation of the lever-side outer ring 114, in other words, pumping operation of the operation lever.
In the brake-side clutch section 112 having the above-mentioned structure, when the rotational torque is reversely input to the output shaft 122, the cylindrical rollers 127 are engaged into the wedge gaps 126 formed between the output shaft 122 and the brake-side outer ring 123 so that the output shaft 122 is locked with respect to the brake-side outer ring 123. In this manner, the rotational torque reversely input from the output shaft 122 is locked by the brake-side clutch section 112, and thus back-flow of the rotational torque to the lever-side clutch section 111 is interrupted.
In the brake-side clutch section 112, when the rotational torque is input from the lever-side clutch section 111 to the inner ring 115, on the other hand, the inner ring 115 is brought into abutment on the cylindrical rollers 127 and presses the cylindrical rollers 127 against the elastic forces of the plate springs 128. As a result, the cylindrical rollers 127 are disengaged from the wedge gaps 126 formed between the brake-side outer ring 123 and the output shaft 122 so that the output shaft 122 becomes rotatable. When the inner ring 115 is further rotated, the rotational torque is transmitted from the inner ring 115 to the output shaft 122, and the output shaft 122 is rotated.